Lithium secondary cells are widely used for portable electronic devices, personal computers, and so on. Therefore, there are needs for advanced miniaturization and weight lightening in such a lithium secondary cell, as well as increased energy densities for highly-functional electronic devices and long-life and reduced cycle deterioration during charge/discharge. Such a lithium secondary battery has a structure configured by opposite-disposing a negative electrode active material layer having a negative electrode active material formed on a current collector and a positive electrode active material layer having a positive electrode active material formed on a current collector therebetween a separator, filling an electrolytic solution to immerse them, and sealing the outer body within an outer body wherein the negative electrode active material and positive electrode active material are capable of absorbing and releasing reversibly lithium ions during charging/discharging.
As this kind of negative electrode active material, in terms of a high energy density, a low cost and safety, silicon, silicon oxide, metals such as tin forming an alloy with lithium, and metal oxides instead of carbon-based material are used. However, in a case of a negative electrode active material layer containing silicon, expansion and contraction in volume according to charge and discharge are large, and according to repetition of charge and discharge due to reaction with an electrolytic solution, falling of fine powder from the negative electrode active material layer, or the like may occur, resulting in a reduction in the capacity of a cell. Particularly, in a case of a cell using silicon or silicon oxide as a negative electrode active material, if the cell is used under a high-temperature environment of 45° C. or more, a reduction in the capacity of the cell is large and in a stacked laminate type cell, deterioration tends to be remarkable.
In order to suppress this deterioration according to charge and discharge, there have been reported a negative electrode using carbon material particles, silicon particles, and silicon oxide particles as negative electrode active materials (Patent Document 1), a negative electrode using particles having carbon coating films on the surfaces of silicon dioxide particles in which silicon is dispersed, as a negative electrode active material (Patent Document 2), and so on.
Meanwhile, in order to improve cycle property, specific materials have been added in electrolytic solutions. As specific examples of these additives, there have been reported benzoic anhydride, phthalic anhydride, maleic anhydride (Patent Document 3), specific succinic anhydride or the like (Patent Document 4), and specific maleic acid derivatives or the like (Patent Documents 5 and 6).
With respect to lithium secondary cells, it is required to increase capacities, suppress reductions in capacities with respect to use under high-temperature environments, improve cycle properties, and increase lives.